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Application of biokinetic model in studying the bioaccumulation of cadmium, zinc, and copper in the scallop chlamys nobilis

Authors Pan, Ke
Issue Date 2009
Summary Few studies were carried out on metal biokinetics in scallop which is of economic and ecological importance. A series of experiments were conducted to investigate the trace metal biokinetics and bioaccumulation in the scallop Chlamys nobilis both in the laboratory and field, using biokinetic model and subcellular fractionation as major tools. Allometry (effect of body size) greatly affected Cd and Zn concentrations in the scallop C. nobilis and their underlying biokinetic mechanisms. The efflux rate of Cd for the scallop was significantly lower than those found in other bivalves and growth dilution appeared to be important in the overall metal accumulation in this species of scallop. The modeling suggested that the very high AE and relatively low efflux rate for Cd explained the high Cd concentrations in the scallop C. nobilis. Dietary uptake dominated the overall Cd and Zn accumulation in the scallop C. nobilis. Our results showed that, in general, both Cd and Zn were sequestered in insoluble forms (organelles, metal-rich granules, and cellular debris). The main binding pool for the acquired metals was organelles for Cd and cellular debris for Zn. Storage in the non-toxic form both in organelles and metallothionein-like protein (MTLP) instead of through exocytosis was the major detoxification strategy to control Cd and accounted for the low efflux rate of Cd from scallop. An active transplantation experiment was carried out in Hong Kong waters under complex environmental conditions to investigate the inter-relationship among food quality, ingestion rate and growth in controlling the bioaccumulation of metals in the scallop. The results confirmed that scallop accumulated metals differently in different marine environments with comparable ambient metal concentrations. Food quality not only influenced their assimilation of metals but also their clearance rates. The ingestion rate together with the growth rate was shown to have an effect on the bioaccumulation of metals. Significant intraspecific and interspecific variability of metal bioaccumulation in bivalves were observed in our study. Contrasting metal efflux rates and metal subcellular distributions among different individuals were found to be important factors affecting the intraspecific heterogeneities of Cd and Zn bioaccumulation. Our study demonstrated that Cu biokinetics in five species of bivalves was species-dependent and contributed to the different body burdens of Cu in bivalves. Among all the biokinetic parameters, the efflux rate appeared to play a key role in determining the interspecific and intraspecific differences in the concentrations of Cu in the bodies of bivalves. Differences in the efflux rate among bivalves were significantly related to the distribution of Cu in the MTLP fraction, strongly suggesting that MTLP was involved in Cu regulation and elimination in bivalves.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009
Language English
Format Thesis
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